Shearer is convinced that the Magpies will be relegated, after watching their dire performance in a 3-1 defeat against Bournemouth at the weekend.
And the Tyneside legend is concerned that Newcastle’s slide is only just starting, as he fears next season could be even worse.
“Steve was very lucky to get this job after overseeing Derby’s implosion last season,” McClaren said.
“For some time now he has looked powerless to stop a slide into the Championship. Because that is where I am convinced my club is heading now.
“And don’t believe that the size of the club means they will be bouncing back any time soon either. They could go right through the Championship as well, because there are barely any characters in this side who would fight to get the club back up. They simply do not care.
“They have betrayed a club, a city, a community, with their lacklustre and totally heartless performances.”
Newcastle’s display against Bournemouth was absolutely terrible and it extended their run of poor form.
The North East side have lost nine of their last 12 matches and they are currently stuck in 19th place in the Premier League table.
Although McClaren’s side are only one point adrift of safety, they have shown few signs of encouragement in recent weeks.
Newcastle’s next match comes against top of the table Leicester City next Monday evening.